Feeding mechanism for an automatic gun



July 15, 1969 E; M. sTONER FEEDING MEcHAnIsM FOR AN AUTOMATIC GUN FiledSept. 29, 1965 11 Sheets-Sheet 1 INVENTOR, 06E/VE M .S70/V51?.

f GAMBHELL A 7- roeA/f ys.

July 15, ISGS E. M. sTNl-:R

FEEDING MECHANISM FOR AN AUTOMATIC GUN Filed sept. 29, 1965 11Sheets-Sheet 2 E. M. STONER l1 Sheets-Sheet 5 TTAA/E/S'.

July 15, ISGS FEDING MECHANISM FOR AN AUTOMATIC GUN Filed sept. 29. 1965July 15, IQGQ E. M. sToNER FEEDING MECHANISM FOR AN AUTOMATIC GUN Filedsept. 29, 1965 1l Sheets-Sheet 4 July 15, E. M. sToNER FEEDING MECHANISMFOR AN AUTOMATIC GUN Filed sept. 29, 1965 ll Sheets-Sheet 5 ArrofA/y'siJuly 15, 1969 E. M. sToNER FBEDING MECHANISM FOR AN AUTOMATIC GUN Filedsept. 29, lees ll Sheets-Sheet 6 T/MMMMNRM 74,/

INVENTOR EUGENE' M S70/V51? BY fwn 5f; ,YA/0555 f GMH/YELL Arron/5K5'.

QMN mwN NNN E. M. STONER FEEDING MECHANISM FOR AN AUTOMATIC GUN FiledSept. 29, 196.5

July 15, 1969 11 Sheets-Sheet 7 mmwwww, w. m E www www QN MN ML @WWI/MNJ u L. www mm 0 1 E. www .1 v5 N5 NQ l a mM. E 6M E M e. 6 MG M Y? July15, 1969 E. M. sroNE-R FEEDING MECHANISM FOR N AUTOMATIC GUN Filed Sept.29, 1965 11 Sheets-Sheet 8 f/ 6 1520i/ 'n l 657 m W Lm z 4 25?@ aga/75ma M 2 9 225 2 Z/@Sfn d JC sa.: 6% o o .n 2,/v

y @m m,

2K6@ i f INVENTOK 06E/VE M S70/V61?.

E 5` w o/ N N ear MMA W@ July 15, 1969 n E. M. STONER 3,455,204

FEEDING MECHANISM FR AN AUTOMATIC GUN Filed Sept. 29. 1965 l1Sheets-Sheet 9 BYF 51 AfA/055.5

@Anfrage-L July 15, 1969 E. M. sToNER FEEDING MECHANISM FOR AN AUTOMATICGUN Filed Sept. 29, 1965 ll Sheets-Sheet l0 MS NN www ww @www INVENTOR.EUGENE M S70/VEA? July l5, 1969 E. M. STONER A3,455,204

FEEDING MECHANISM FOR AN AUTOMATIC GUN Filed Sept. 29, 1965 llSheets-Sheet 11 EUGENE M S70/VEP Byron/1.5@ AfA/0555 f caaMeE/ L ATTUPNE/ United States 3,455,204 FEEDING MECHANISGRIJ FOR AN AUTOMATICABSTRACT OF THE DISCLOSURE A recoil-operated gun adapted for mounting ona vehicle includes a dual feed mechanism which permits selection ofammunition from either of two stores fed through separate trays onopposite sides of the receiver. A reciprocating bolt carrier has arelatively long portion offset from the barrel axis and a relativelyshort portion in line with the barrel axis. The long portion drives apair of cam operated pawls which alternatively engage rounds inwhichever tray is pivoted to the operative position. A recoil mechanismforward of the bolt carrier has means for accelerating the bolt carrierand bolt relative to the barrel, and means for buffering the recoil andcounter-recoil force of the barrel including a throttling by-passorifice which varies in effective size as the barrel reciprocates. Abuffer assembly rearward of the bolt carrier is engaged by the carriershort portion to buffer the forces of the bolt carrier recoil and theempty cartridge ejection, and to return the bolt to battery. The springsof the buffer assembly also act in the opposite direction to buffer theimpact of sear engagement with the bolt carrier.

'I'his invention relates to automatic guns and more particularly, torapid firing, short recoil-operated, automatic guns.

In order to be suitable for field use, particularly as a militaryweapon, a rapid-firing automatic gun not only must fire satisfactorily,but also should be easy to repair and maintain in the field with aminimum of tools. Toward this end, the gun should be as simplyconstructed and have as few parts as is consistent with a high standardof performance.

Further, guns designed to be mounted on military vehicles, e.g. armoredcars, should be relatively compact and light as compared with stationaryguns. The size of that portion of the gun from the ammunition feedingtray or magazine rearward is particularly critical because the rear endof the gun, including usually the ammunition feeding tray as well,extends within the cupola of the armored car. Since the gun is traversedto aim it, the space which must be allowed for the gun inside thevehicle increases rapidly with the distance from the tray rearward.

The gun which comprises this invention can be field stripped easily andquickly by one man without tools. Many of the parts of the gun servemultiple functions so that the weight, size and complexity of the gun isreduced, maintenance is facilitated, and reliability increased. Theparts are arranged to minimize particularly the size of the gun portionwhich must be contained within a vehicle.

Generally, in accordance with this invention, the automatic gun isrecoil-operated. The gun barrel reciprocates axially in a receiverforward of an ammunition feeding station in the receiver. A bolt isreciprocated axially past the feeding station by a bolt carrier whichhas a relatively short upper portion and a lower portion which is longerthan the bolt carrier stroke. A cam follower on an ammunition feedingmeans cooperates with a cam extending along the length of the boltcarrier lower portion to feed ammunition to the feeding station.

A recoil assembly, which is disposed beneath the barrel 3,455,204Patented July 15, 1969 and forward of the bolt carrier, is operablycoupled between the barrel and receiver for buffering recoil andcounter-recoil forces. Further, the recoil assembly is responsive tobarrel recoil for engaging the forward end of the bolt carrier lowerportion to accelerate the bolt carrier in recoil relative to the barrel.A buffer assembly at the rear of the receiver engages the rear of thebolt carrier upper portion to buffer the recoil force of the bolt andbolt carrier.

In an exemplary embodiment of this invention, a scar assembly at therear of the receiver, which is selectively engageable with a sear notchon the bolt carrier body to interrupt the forward stroke of the boltcarrier is buffered by the same buffer assembly as buffers the recoilforce of the bolt and bolt carrier.

This invention also includes several novel sub-combinations which, whileparticularly useful in the gun combination described above, are alsouseful in other automatic rapid firing guns. For example, in accordancewith one aspect of the invention, the recoil means includes a uidcylinder fixed to the receiver and located below the barrel in alignmentwith the lower portion of the bolt means. The internal walls of thecylinder define a large diameter forward portion in which a recoilpiston reciprocates, and a smaller diameter rearward portion in which anaccelerator piston reciprocates. The recoil piston is fixed to thebarrel, and the accelerator engages the forward end of the bolt carrierlower portion to accelerate it in recoil relative to the barrel.`

The accelerator piston bottoms out after the barrel has completed aninitial part of its recoil movement, and a restricted bypass openingpermits the recoil piston to continue rearward a short distance,buffering the barrel recoil force.

This invention further includes a selective ammunition feeding systemparticularly useful with the gun described above, but also useful withother guns. Prior art automatic guns commonly used by the military haveused a single store of ammunition for feeding the gun. Since differenttypes of targets require different types of ammunition, e.g. highexplosive ammunition for personnel,

'and armor piercing ammunition for armored vehicles,

such prior art guns have created problems. Often such prior art gunsused a single type of ammunition which was a compromise between thetypes desired, or was designed to be effective against only a limitedtype of target. Other times, plural types of ammunition were mixed on asingle feed belt so that all types of ammunition were fired at alltargets. It is evident that neither of these situations wassatisfactory.

The selective feeding feature of this inven-tion permits rapid selectionof the proper type of ammunition for each target, thus increasing theflexibility of the gun and eliminating wasteful firing of ineffectiverounds. Generally in accordance with this aspect of the invention, theammunition feed means is coupled to rounds of ammunition from aplurality of different stores, and includes selector means for selectingany one of the ammunition stores to supply ammunition to the receiver.

In an exemplary embodiment, the bolt means which reciprocateslongitudinally in the receiver past the feeding station has a relativelyshort upper portion and a rela-- tively long lower portion, the lengthof the lower portion exceeding the stroke of the bolt means. An elongatecam slot is formed in each of two opposite sides of the lower portion ofthe bolt means. The ammunition feeding means has a pair of cam followerseach of which cooperates with a respective one of the cam slots tooperate an ammunition feed pawl means. Each ammunition feed pawl meansis effective to feed ammunition from a different store, and the selectormeans are operative to alternatively select either of the ammunitionstores.

As the optimum ballistic characteristics for each type of ammunitionoften differ, the ballistic characteristics of the ammuntion in each ofthe plural 'stores will often be different. In yet another aspect, thisinvention takes these differing characteristics into consideration byproviding a gun sight means which is automatically adjusted responsiveto the store selected.

These and other objects and features of this invention will be apparentfrom the following description when read with reference to theaccompanying drawings 1n which:

FIG. 1 is a perspective view showing the preferred embodiment of a gunconstructed in accordance with this invention;

FIG. 2 is an enlarged sectional view taken generally along lines 2--2 ofFIG. 1;

FIGS. 3a and 3b are fragmentary, enlarged side views, in section,showing portions of the recoil assembly illustrated in FIG. 2;

FIG. 4 is a sectional view taken generally along lines 4-4 of FIG. 3a;

FIG. 5 is a perspective view showing a part of the recoil assemblyremoved from the gun;

FIG. 6 is a sectional view taken generally along lines 6-6 of FIG. 2;

FIGS. 7-9 are fragmentary, enlarged side views, in section, showing thecentral portion of the gun illustrated in FIG. 1 in successive stages ofthe firing cycle;

FIG. 10 is an enlarged sectional View taken generally along lines 10-10of FIG. 2;

FIG. 11 is an enlarged sectional view taken generally along lines 11-11of FIG. 2;

FIG. 12 is an enlarged sectional view taken generally along lines 12-12of FIG. 2;

FIGS. 13-16 are fragmentary, enlarged side views, in section, yshowingthe rear portion of the gun illustrated in FIG. 1 in successive stagesof the tiring cycle;

FIG. 17 is an enlarged, rear elevation view of the gun illustrated inFIG. l with portions cut away;

FIG. 18 is a sectional view taken generally along lines 18--18 of FIG.15;

FIG. 19 is a perspective view of the rear buffer and sear assemblyremoved from the gun;

FIGS. l2O and 21 are fragmentary, enlarged top views, in section,showing the central portion of the gun illustrated in FIG. 1, andparticularly illustrating the ammunition feeding means in successivestages of the firing cycle;

FIG. 22 is a sectional view taken generally along lines 22-22 of FIG.20;

FIG. 23 is a sectional view taken along the same lines as FIG. 22, butshowing the bolt and bolt carrier in the forward position;

FIG. 24 is a perspective view of a portion of an ammunition belt removedfrom the gun;

FIG. 25 is a fragmentary, perspective view of the ammunition feedingmeans with portions cut away;

FIG. 26 is a perspective view of a portion of the arnmunition feedingmeans removed from the gun;

FIG. 27 is a fragmentary perspective view, in vertical, longitudinalsection, showing the central portion of the gun in the counter-recoilpart ofthe cycle;

FIG. 28 is a fragmentary top view, 'in section, similar to FIGS. 21 and22, but showing the ammunition feed selector in an intermediateposition;

FIG. 29 is a side View, in section, showing an alternative embodiment ofthe recoil assembly; and

. FIG. 30 is a diagram of [a circuit for selecting a fully automatic orsemi-automatic firing cycle responsive to the ammunition feed selector.

Referring to FIGS. 1, 2 and 6, an automatic gun is shown, including abarrel 5, a receiver 6, and ammunition feeding means 7. The gun ismounted, e.g. on a vehicle such as a military armored car, by anexemplary means which includes a collar 11 having internal rails 12which tit into conforming external grooves 13 on the side of thereceiver. A removable pin 14 extends through aligned apertures 15, 16 inthe collar and receiver 6 to x the gun longitudinally with respect tothe collar. The collar 11 is supported on a horizontal pivot pin 18 in ayoke 17. A vertical pin 19 extends from the base of the yoke formounting the same on a vehicle (not shown) for pivotal movement about avertical axis. Thus, the gun is positively xed against sliding movementrelative to the vehicle, `but may be pivoted to aim the gun.

The barrel is mounted for reciprocal movement along the axis 26 of itsbore in the forward portion of an elongate, generally cylindrical, upperpart 25y of the receiver. A bolt means or carrier mechanism is providedfor chambering, firing and ejecting rounds of ammunition 27. The boltmeans includes a bolt 28, which is aligned with the barrel axis, and abolt carrier 29 which is attached to the bolt and reciprocateslongitudinally in the receiver past an ammunition feeding station 30located rearward of the barrel. The bolt carrier 29 has a relativelyshort upper sleeve portion 31 which carries the bolt, and a relativelong, lower body portion 32 which is housed in a lower, generallyrectangular, part 33 of the receiver.

A recoil assembly 36 located beneath the barrel is operably coupledbetween the barrel and the forward end of the receiver lower part 33 forbuffering recoil and counter-recoil forces. The recoil assembly isaligned with the `body 32 of the bolt carrier and engages its forwardend to accelerate the bolt carrier 29 in recoil relative to the barrel.

The recoil force of the bolt 28 and carrier 29 is buffered by a bufferassembly 38 at the rear of the receiver which engages the rear of thebolt carrier sleeve 31 near the end of the recoil stroke. A sear 41pivotally connected to the buffer assembly 38 engages in a sear notch 42on the bolt carrier body 32 to interrupt counter-recoil movement of thebolt and bolt carrier and retain them in the rearward cocked position.Depression of a trigger mechanism 40 raises the sear 41 out ofengagement with the notch 42 to fire the gun.

A muzzle brake 43 is connected on the forward end of the barrel topermit gas to escape rearwardly through openings in the brake.

Referring now to FIGS. 6 and 9, as well as to FIG. 2, a breech barrelextension 48 is threaded onto the rear of the main barrel portion. Theexternal surface of the barrel extension forms a bearing surface whichslideably engages an internal bearing surface 49 in the upper forwardportion 25 of the receiver. A collar 50 aixed around the barrel also hasan external bearing surface 51 which slideably engages a correspondinginternal bearing surface 52 in the forward end of the upper forwardreceiver portion 25 to support the barrel. A shoulder 53 at the forwardend of the barrel collar 50 abuts a shoulder 54 intermediate the ends ofthe barrel, and a nut 55 threaded onto the barrel forward of the collarholds the collar in place longitudinally. Tabs 56 on a lock washer 57between the nut 55 and the collar 50 are bent in opposite directionsinto detents on the collar and nut to retain the nut 55 againstaccidental loosening. The collar is fixed against rotation relative tothe barrel by an internal longitudinal key 60 on the collar which isinserted in a corresponding keyway 61 formed in the barrel. A lug 62which depends downwardly from the collar, extends through a forwardlyopen guide slot 63 in the receiver, and engages the sides of the guideslot to fix the collar 50 and barrel against rotation relative to thereceiver, while permitting axial reciprocation.

Referring particularly to FIGS. 2, 3a and 3b, the recoil assembly 36includes a recoil cylinder 70 the forward end of which extends throughan ear 71 depending from the receiver -6 and the rear end 72 of which isthreaded into the front of the receiver lower part 33, so that thecylinder extends parallel to and below the barrel axis 26 in alignmentwith the bolt carrier vbody 32. The recoil cylinder 70 houses a recoilpiston 73 which has a piston head 75 and piston rod 74 extending forwardfrom the head and on through an aperture 76 in the depending portion ofthe barrel collar lug 62. A sleeve nut 77, threaded onto the piston rod74 has an external flange 78 which abuts the barrel collar lug 62 toretain it on the piston rod. Accidental loosening of the sleeve nut 77is prevented by a spring biased plunger 79 which engages in any of aplurality of detents 80 formed around the flange 78 of the nut. Anadjusting nut 83 on the piston rod rearward of the collar lug 62accurately locates the longitudinal position of the barrel relative tothe receiver and recoil mechanism. An arcuate piece of resilientmaterial 85 is wedged into a tapered arcuate slot 86 in the adjustingnut to hold it at any selected place of adjustment along the threads 87of the piston rod.

The sleeve nut is knurled on its external surface so as to facilitateits removal by hand. With the sleeve nut 77 removed, the barrel may befreely slid out the forward end of the receiver.

Because the recoil piston -rod 74 is fixed to the barrel 5 by the sleevenut 77 and adjusting nut 83, the recoil piston head 75 reciprocatesrearwardly and forwardly with the barrel in recoil and counter-recoil,respectively.

The recoil piston head reciprocates in a front bore 91 of relativelylarge internal diameter in the recoil cylinder 70, and an acceleratorpiston 93 reciprocates in a rear bore 92 of smaller internal diameter inthe cylinder. The accelerator piston 93 includes a piston head 95 sealedby an O-ring seal 96. The interior of the recoil cylinder, between therecoil piston head 75 and the accelerator piston head 95, is filled withhydraulic fluid so that as the recoil piston moves rearwardly in recoil,the smaller diameter accelerator piston 93 is driven rearwardly at anincreased velocity.

The accelerator piston 93 is hollow. It has a closed forward extension101 protruding forward from the piston head 95 and also has an open rearextension 107 which protrudes rearwardly from the piston head 95. Inrecoil, the rear extension 107 of the accelerator piston engages thealigned forward end 97 of the bolt carrier body 32 to push the boltcarrier 29 rearward from the battery position illustrated in FIG. 2.Rearward movement of the accelerator piston is limited by an interiorshoulder 108 at the rear end of the recoil cylinder.

A heavy recoil spring 98 interior of the recoil cylinder is compressedbetween a shoulder 99 in the cylinder wall and the recoil piston head tourge the recoil piston 73 forward. The accelerator piston 93 is urgedforward by a lighter return spring 100, which is housed in the hollowaccelerator piston and the closed forward extension 101 thereof nestedwithin the recoil spring 98. The accelerator spring 100 is compressedbetween the closed forward end of the accelerator piston and a plug 102.The plug 102 is slideably mounted within the rear extension 107 of theaccelerator piston and abuts a stop pin 103 which is xed to the recoilcylinder 70 and extends through an elongate slot 104 in the rearextension of the accelerator piston. In its forward position, theaccelerator piston head 95 abuts an annular ring 105 interposed betweenthe shoulder 99 and the recoil spring 98. Since the recoil spring isconsiderably stronger than the accelerator spring, this limits forwardmovement of the accelerator piston.

A wedge-shaped, or tapered, throttling groove 110 (FIGS. 3a and 4) isformed in the wall of .the large diameter part of the recoil cylinder.The throttling groove 110 permits a programmed amount of uid to bypassthe recoil piston head after the recoil piston head has moved a selecteddistance rearward in recoil. An annular spacer 111 (FIGS. 3a and 5)having forwardly extending spaced-apart fingers 112 is interposedbetween the forward end of the recoil spring and the recoil piston headto provide radial passageways 113, assuring that fluid communicationbetween the throttling groove 110 and the uid in the chamber portionrearward of the piston head 75 is not blocked off by compression of therecoil spring 98. Sealing of the bypass is a particular problem becausethe high acceleration encountered in rapid ring automatic guns causesthe recoil spring to compress dynamically, with the greatest amount ofcompression in the forward portion adjacent the recoil piston head atthe initial stages of recoil.

The chamber within the recoil cylinder 70 is sealed at the rear end bythe accelerator piston head seal 96. At the forward end, the chamber iseffectively terminated by a threaded plug 115 through which the recoilpiston rod 74 extends in engagement with an O-ring seal :114. The recoilpiston head 75 divides the chamber within the recoil cylinder into arear chamber and a forward chamber. The recoil piston head isapproximately the same diameter as is the forward bore 91, but there isno seal between the piston head and bore. Air may be bled from thecylinder chamber by backing off a set screw 116 to unseat a ball valve117 inthe plug 115.

A bellows-type cover 118 extends between the plug 115 and the adjustingnut 83- to enclose the extended sealing surface of the recoil piston rod74.

The recoil piston head 75 has a check valve 122 formed thereon tofacilitate the return of the barrel to battery position in time toreceive the next round. The check valve 122 opens on forward movement ofthe recoil piston to permit fluid to flow rearwardly through a pluralityof small orifices 123 in the recoil piston head. The valve 122 includesan annular ilappe-r ring 124 which is seated by a spring 125 compressedagainst an outwardly extending shoulder or cap 126 fixed on a centralrear extension 128- on the recoil piston head, to seal the orifices 123except during forward movement of the piston head.

Belleville or cup counter-recoil springs 127 stacked in series-parallelforward of the recoil piston head cooperate with the piston head and theplug 115 to buffer counterrecoil forces.

The recoil piston rod 74 is hollow to provide a reservoir forreplenishing hydraulic fluid in the chamber of the recoil cylinder, andt0 accommodate thermal expansion of the fluid. A replenisher piston 130is slideable in the reservoir chamber 131 and sealed by an O-ring 132around the piston head 133. The replenisher piston is biased rearwardlyby a replenisher spring 134 'which surrounds the replenisher piston rod135 and abuts a cap 136 retained in the forward end of the recoil pistonrod 74.

If the volume of hydraulic fluid in the recoil cylinder decreases,either through temperature decrease or leakage, the differentialpressure between the reservoir 131 and the main chamber 94 opens aspring-biased ball check-valve 138 in the piston head to provide aconduit through which uid may flow to replenish the supply in the recoilcylinder.

On the other hand, as the temperature of the hydraulic fluid in therecoil cylinder increases, the hydraulic fluid seeps forward around therecoil piston head, which is not sealed against the walls of thechamber. yIt passes through a small bleed hole 139 in the wall of therecoil piston rod and into the replenisher reservoir, thus forcing thereplenisher piston 130 forward against the replenisher spring. Thereplenisher spring 134 is considerably weaker than the acceleratorspring V100, so that expansion of the hydraulic fluid will cause thereplenisher piston, rather than the accelerator piston 93 to move.

If expansion of the uid is great enough, the replenisher piston movesforward of a radial outlet 140 through the side of the recoil piston rodso that fluid seeps out between the threads of the adjusting nut 83 andthe recoil piston rod. The external surface 141 of the recoil cylinderis circumferentially ridged to provide an increased cooling surface, anddecrease the likelihood of overexpansion.

Because the bleed hole 139 is quite small land the recoil cycle time isextremely short, the replenisher piston does not move substantiallyunder the influence of the instantaneous pressure increase in the mainfluid chamber 94 caused by recoil of the recoil piston.

The distance which the replenisher piston rod 13-5 extends forward outof the recoil piston rod 74 is proportional to the quantity of hydraulicfluid in the recoil cylinder; hence, the replenisher piston rod servesas a dipstick to indicate the supply of fluid by index marks (not shown)on the dipstick which are visible through an aperture 142 in the sleevenut 77.

Referring particularly to FIGS. -12 and 27, as well as FIG. 2, as thebolt carrier 29 reciprocates, two laterally spaced legs 148 on theforward end of the bolt carrier body 32, and two laterally spaced legs149 on the rear of the body 32 are guided in longitudinal trackways 150formed in the bottom plate 151 of the receiver 6. Raised bearingsurfaces 152, 153 and 154 located on the upper side of the body 32 atthe forward end, the center 153, and the rear end 154 thereofrespectively, slidingly engage the bottom surface of parallel elongateguide rails 155 which are mounted interior of the sides of the receiver.The sides of a neck portion 156 of the bolt carrier, which integrallyconnects the upper sleeve portion 31 to the lower body portion 32, bearagainst the sides of these rails 155 to x the top of the bolt carrierlaterally with respect to the receiver. Thus, as the Ibolt carrierreciprocates longitudinally in the receiver, the guides maintain thebolt in axial alignment with the barrel.

Referring particularly to FIGS. 7, 10 and 27, external locking lugs orteeth 160 at the forward end of the bolt engage with internal lockinglugs or teeth 161 at the rear end of the barrel extension to lock thebolt to the barrel when the bolt is in battery. When the bolt is rotatedfrom the locking position to a position in which the teeth 160 on thebolt are aligned with the spaces between the teeth 161 on the barrelextension, the bolt is unlocked and may be reciprocated rearwardly awayfrom the barrel.

Referring now particularly to FIGS. 7, 11 and 27, the bolt 28 isinserted in the sleeve portion 31 of the bolt carrier for axial androtative movement, and connected to the sleeve by a cam follower pin 162extending through the bolt and into radial 4surface cam slots 163 onopposite sides of the bolt carrier sleeve. The cam pin is held in placeby the interior walls of the receiver 6. The forward and rearwardportions of the cam slots are parallel to the barrel axis to permitlimited axial movement of the bolt in the carrier sleeve-with the boltin the aligned position Iwhen the cam follower pin 162 is in the forwardportion of the slots and in the locked position when the cam followerpin is in the rear portion. The central portion of the cam slot isoblique to the bolt axis to rotate the bolt between the locking positionand the aligned position. Thus, as the bolt carrier body is acceleratedrearwardly relative to the barrel by the recoil mechanism 36, the camfollower pin cooperates with the cam slot to rotate the bolt to thealigned position, and then carry the bolt rearward with the boltcarrier.

When the bolt leaves the barrel it is in the aligned position, and isextended forward in the sleeve. As is shown in FIGS. 7, 13 and 18, aspring-biased crevice pin 165, mounted in the bolt carrier neck andsleeve for radial movement with respect to the barrel axis, is urgedupward into a notch 166 in the bolt to hold the bolt forward in thesleeve, and therefore in the aligned position. A cam follower or rampingpin 167 extends outwardly from the crevice pin and rides on elongate camsurfaces formed on the top of the guide rails 155 to hold the crevicepin in the upward, engaged position after the bolt is out of battery sothat the bolt remains extended despite forces on it from stopping thebolt carrier at he rear of the receiver and from stripping rounds duringthe counter-recoil stroke. The forward edge of the crevice pin 165 isbeveled so that the bolt forces the crevice pin out of engagement whenthe bolt returns to battery and strikes the barrel, while the sleeve 31is still moving forward in counter-recoil.

An extractor claw 168 extends forward of the bolt to grip the lip 169 ofa cartridge case. The claw 168 is connected to the bolt by a pivot pin170 and urged into the gripping position by a spring 171. A beveledsurface 172 on the leading edge of the claw causes it to ride up overthe lip of a cartridge as the bolt moves forward to engage a cartridge.A firing pin 173 is afxed to the rear end of the bolt carrier sleeve bya pin 178 held in place by the walls of the receiver 6. The firing pin173 extends slideably through a bore 174 in the bolt. A cartridgeejecting rod or pin 175 also extends slideably through a bore 176 in thebolt and an arcuate aperture 177 (see FIG. 12) in the rear end of thebolt carrier sleeve. The ejecting pin 175 is caught between the bolt andcarrier sleeve by an enlarged shoulder 180 formed intermediate its endsand accommodated by aligned recesses in the bolt and sleeve.

Referring particularly to FIGS. 15 and 19 the buffer assembly 3S at therear of the receiver includes a plurality of annular cup or Bellevillesprings 182 stacked in series and aligned with the bolt carrier sleeve31. The Belleville springs 182 are housed in a cylindrical sleeve 183mounted for longitudinal sliding movement at the rear of the receiver.The sleeve has an integral rear end plate 184 which abuts the back plate185 of the receiver. A plunger 186 is longitudinally slideable in theforward end of the sleeve and is held against the Belleville springs bya stop or screw 187 slideably extending through the plunger 186 and endplate 184 and threaded into the back plate 185 of the receiver. Thescrew may be tightened or loosened, as desired, to adjust thepre-loading of the Belleville springs 182.

As the bolt carrier nears the end of its recoil stroke, the rear face190 of the bolt carrier sleeve engages the plunger 186 and compressesthe Belleville springs 182 rearwardly against the end plate 184 of thebuffer sleeve to gradually stop the recoiling bolt and bolt carrier. TheBelleville springs then expand and shoot the bolt and bolt carrierforward toward the battery position for tiring another round.

The sear 41 is pivotally mounted on the lower side of the buffer sleeveintermediate the ends of the sleeve by a pin 192 extending throughapertures in a pair of lugs 193 affixed to the sleeve. A compressionspring 194 engaged between sleeve 183 and the sear urges the seardownward into engagement with the sear notch 42 formed in the uppersurface of the bolt carrier body 32 near the rear end of the body.

The trigger 40 is mounted on the rear plate 185 of the receiver by apivot pin 195. The trigger has a forward portion 44 which extends into anotch 45 formed in the rear end of the carrier body 32 (FIG. 27) so thatthe forward portion of the trigger underlies the sear. The trigger maybe activated manually or by a solenoid 196 to hold the sear up out ofengagement with the sear notch so that the bolt carrier will return tothe battery position. If the trigger is released, the spring 194 urgesthe sear downward to engage in the sear notch and interrupt thecounter-recoil stroke of the bolt carrier, thereby holding the boltcarrier in the rearward cocked position. The sear force is buffered bythe sleeve 183 compressing the Belleville springs 182 forward againstthe screw head 188 and plunger 186 as the sleeve 183 slides forward inthe receiver (FIG. 16).

Referring particularly to FIGS. 7, 9 and 13, a long operating spring 200extends through an opening 201 in the bolt carrier body 32 and iscompressed between the back plate 185 of the receiver and the forwardpart of the bolt carrier body 32 to drive the bolt carrier forward. Theoperating spring 200 is guided on a rod 202 which is aflixed to the backplate of the receiver by a pin 203 and extends slideably through a bore204 in the front end of the carrier body 32. A keeper 233 is slideableon the rod 202 and is retained by an enlarged head 234 on the forwardend of the rod. The forward end of the guide rod 202 extends into theopen rear end '7 of the accelerator piston 93 to support the rod whenthe bolt carrier is rearward from the battery position.

A charging system is provided for pulling the bolt carrier from thebattery position rearward to the cocked position. As seen in FIGS. 1, 2and 7 through 12, the charging system includes a chain 205 which isnested between the pairs of bolt carrier legs 148, 149 and extends alongthe receiver through a central way 206 formed in the bottom plate 151 ofthe receiver 6. The forward end of the lchain is connected to a chargingblock 207 which freely engages the forward end of the bolt carrier body32 as the chain is pulled rearwardly. The block 207 travels along theway 206 on a guide rod 208 which extends through an aperture 209 in theblock into an aperture 210 at the forward end of the receiver. The rearend of the charger guide rod is alixed to the receiver by a support 211extending up from the bottom plate. The chain is engaged by a sprocket215 journaled on the bottom plate at the rear of the receiver. Thesprocket may be rotated by a removable manual crank 216 (see FIGS. 1 and17), or by a powered means (not shown). An elongate spring 220 is guidedon the rod 208 and returns the block 207 to the forward position.

Referring to FIGS. 13 and 17, the back plate 185 of the receiver isconnected to the receiver by upper and lower removable pins 217extending through ears 218 on the receiver and brackets 214 on the backplate. With the pins 217 removed, the back plate may be removed from thereceiver along with the trigger 40, the solenoid 196, the buffer 38,sear 41 and the bolt carrier operating spring 200 and guide rod 202, allof which are attached to the back plate. The bolt 28 and bolt carrier 29are then free to be pulled out the rear of the receiver whereupon thevarious pins 162, 178 are no longer retained by the surfaces of thereceiver and the bolt is easily removed from the carrier anddisassembled.

As is shown most clearly in FIGS. 1, 11, -23, 25 and 27, the ammunitionfeeding means 7 includes similar right and left hand ammunition guidesor feeding trays 228, 229 disposed on opposite sides of the receiver `6at the feeding station 30. Each of the feeding trays 228, 229 guidesrounds 27, 27a, 27b, etc. of ammunition from a different store to thefeeding station 30.

The two ammunition feeding trays 228, 229 are pivotally attached to thereceiver by a pair of vertical mounting rods 219 forward of the tray,each extending through upper and lower ears 221 on the trays and upperand lower brackets 223 on the receiver. As seen in FIG. 11, typicallyeach mounting rod 219 has an upper portion 222 spring loaded intelescoping relationship with a lower sleeve portion 224. The twofeeding trays are interconnected or ganged at their rear ends by upperand lower horizontal connecting bars 225, 226 which slide throughcorresponding keyways 227 transverse to the receiver as the trays pivotabout the forward mounting rods 219. The connecting -bars 225, 226 areconnected to the trays by vertical rear mounting rods 230 which aresimilar to the front mounting rods 219 and which extend through alignedapertures in the bars and in upper and lower brackets 232, 235 extendingrearwardly from the respective trays. Each of the feeding trays can beremoved from the receiver by telescoping the mounting rods 219, 230 toremove them from the respective brackets.

In FIGS. 20-23, 25 and 27 the right-hand tray 228 is shown in theoperative or feeding position adjacent the receiver, and the left-handtray 229 is pivoted away from the receiver to the disengaged position. Aselector is provided for pivoting one or the other of the gangedammunition feeding trays to the operating position to select eed fromeither of the ammunition stores. The selector includes a selector handle236 pivotally connected by a telescoping mounting rod 237 to brackets238, 239 fixed on the receiver rearward of the right-hand tray. Theselector handle 236 is operably connected to the right reartray-mounting rod 230 by upper and lower angle selector levers 240, 241which pivot with the selector handle 236 about the selector mounting rod237. One end of each lever 240, 241 is affixed to the selector handle236, and the other end has a forward opening slot 242 which receives theend of the right rear ammunition tray mounting rod 230. As the selectorhandle is pivoted rearwardly about the selector mounting rod 237, theangle levers 240, 241 cause the ammunition feeding tray connector bars225, 226 to move to the right, thus pivoting the right-hand ammunitionfeeding tray laterally out of the operable position and the left-handammunition feeding tray laterally into the operable position, as isshown in phantom in FIG. 20.

A trigger-type latch 245 (see also FIG. 17) housed in the selectorhandle and pivotally mounted thereon at 246, has an arm 247 with anindexing tab 248 on its upper side to engage in any of three indexingnotches 249, 250, 251 in the upper bracket 238. Thus, the ammunitionfeeding trays are pivoted so that the right-hand tray is in operableposition when the forward notch 249 is engaged, the left-hand tray is inoperable position when the rearward notch 251 is engaged, and both traysare out of operable position when the intermediate notch 250 is engaged(see FIG. 28). The latch 245 is urged into the engaging position by aspring 252 interior of the selector handle and is released by squeezinga depending arm 253.

As the type of ammunition in one tray may have different ballisticcharacteristics than the ammunition in the other tray, means areprovided for adjusting a gunsight responsive to the selection of a feedtray. The sight includes a forward bead 255 and a rear peep sight blade256. Referring particularly to FIGS. 14 and 25, rear sight blade 256 ismounted for vertical sliding movement in a channel shaped bracket 254fixed atop the receiver with the forward side of the bracket being open.A cam follow 257 on the sight blade engages in a cam slot 258 formed ina horizontal channel bracket 259 xed on the connector bar 225 andabutting the front face of the vertical bracket 254, so as to raise therear sight when the left tray is operative and lower the rear sight whenthe right tray is operative in accordance with the predeterminerdifferent ballistic characteristics of the two types of ammunition.

Referring to FIGS. 22-24 the rounds of ammunition 27 are interconnectedby an exemplary disintegrating link 262, the details of which do notform a part of this invention except as the links cooperate with the gunand feeding means of this invention. The belts of ammunition of eachstore are fed up through the ammunition trays alongside the receiver andthen laterally inward through side discharge openings 263 in each trayand through opposite side openings 265 in the upper portion of thereceiver which define the feeding station 30 of the receiver. From theammunition feeding station, the rounds of ammunition are stripped andchambered by the reciprocating bolt as will be described hereinafter.The links 262 continue upward through top openings 266 in the top ofeach ammunition feeding tray where they separate from the belt and fallfrom the gun.

The ammunition feeding means 7 includes similar cam rollers 270 whichcooperate with similar elongate inclined cam slots 271 formed onopposite sides of the bolt carrier body 32 to operate the feedingmechanism. The bolt carrier body 32 and cam slots 271 are longer thanthe stroke of the bolt carrier so the cam followers 270 remain in theslots 271 throughout the stroke. The feeding mechanisms on oppositesides of the receiver are similar; hence, similar reference numeralswill `be used for the corresponding parts of both.

Referring to FIG. 25, as well as to FIGS. 22 and 23, each cam follower270 is approximately centered at the feeding station 30 (see FIG. 2) andis rotatably mounted on a pawl carrier 272 by a horizontal axle 273 nearthe longitudinal center of the carrier. Each of the pawl carriers 272 isinterposed between the bolt carrier body 32 and one of the ammunitionfeeding trays. The pawl carrier 272 reciprocates vertically toward andaway from the feeding station in a rectangular opening 274 formed in theside of the receiver. Elongate tongues 275 on the forward and rear edgeof the pawl carrier engage in corresponding vertical grooves 276 in theside of the receiver to guide the pawl carrier in its verticalreciprocation. A pair of similar feed pawls 277 are each pivotallymounted on the pawl carrier, one forward of the cam follower 270 and onerearward. The pawls 277 are spring biased outward to protrude throughvertical slots 278 in the inboard sides 279 of the correspondingammunition feeding trays and engage the rounds of ammunition containedin the tray. The pawls are free to pivot upwardly but downward pivotingof the pawls is limited by the lower end of each pawl abutting the innerwall 280 of the pawl carrier.

As the bolt carrier moves forward, the feed pawls 277 reciprocatedownward from the position shown in FIG. 22 to that shown in FIG. 23,being cammed inwardly by a round of ammunition 27c as they pass it. Whenthe bolt carrier is in its forward position, the feed pawls are beneaththe round of ammunition 27C to be engaged because the pawl springs 282have biased the pawls outward. The pawls raise the round 27a` in theammunition tray as the bolt carrier returns rearward.

A pair of identical inwardly extending, spring loaded retaining pawls283, only one of which is shown in FIG. 25, are pivoted up out of theway by the round of ammunition 27C as it rises. Then the retaining pawlsreturn beneath the raised round 27C to retain it in place while the feedpawls reciprocate downward to engage the next round 27d. The retainingpawls are each pivotally mounted on a support 284 which is on theoutboard side of the feeding tray, and are biased inward by sprin gs 285to engage the rounds. Downward pivoting of the retaining pawls islimited by abutment of their lower ends 286 (see FIG. 26) against thesupport 284.

An upwardly and inwardly extending plate spring 288 guides the upperround 27a laterally to the feeding station 30, from where it isstripped, chambered and fired. One end of the guide spring 288 is aixedto a rod 290 extending between a pair of spaced guide arms 291 (see alsoFIG. 26). The other end is attached to the upper end of the ammunitiontray; and the center of the plate is bent around a rod 292 which is xedto the support 284 and on which the guide arms 291 are pivotallymounted.

The side opening 263 in each tray has a rear portion 302 which isnarrower than the diameter of the rear part of the round 27 and aforward portion 300v which is wider than the widest part of the round27. The opening 263 is contiguous with an opening 301 in the forwardwall of the tray. The raised round 27 is held in the tray since itcannot pass completely through the narrow rear portion 302 of theopening. However, the round 27 does protrude far enough through the sideopening 263 of the tray, under the urging of spring plate 288, that ifthe tray is in the operating position, the bolt 28 engages the rear ofthe round as the bolt comes forward. The bolt 28 strips the round 27 outof the links 262 and rams the round forward and inward through theforward portion 300 of the side opening 263 and the opening 301 into thechamber of the barrel.

The empty links 262 are guided up out of the openings 266 in the top ofthe ammunition trays by forwardly and rearwardly extending tabs 293 onthe links (see FIG. 24) which engage in vertical guide grooves 294 inthe upper end of the spaced guide arms 291.

A positioning stop 295 engages the round 27a at the feeding station 30to positively limit upward movement of the round and x it at the feedingstation. This stop is pivotally mounted about a horizontal transverseaxis on the upper plate 296 of the ammunition tray so that as the roundmoves forward to the chamber, the stop is cammed forward out of the wayby the cartridge case. A spring 297 returns the stop to its operativeposition. The forward end of the round is guided into the chamber by aramp guide 2-99 on the forward end of the ammunition tray and taperedsurfaces 298 on the locking teeth 161 adjacent opposite sides of thebarrel extension (see FIG. 21).

When an ammunition tray is pivoted to the inoperative position, as forexample the left-hand tray in FIGS. 22 and 23 and both trays in FIG. 28,the feed pawls will continue to reciprocate vertically as the boltcarrier reciprocates, but the rounds of ammunition in the tray are farenough outboard of the feed pawls that the pawls do not engage therounds, and no ammunition is fed from that tray. The top round is heldin the tray since it cannot pass through the rear portion 302 of theside opening 263 far enough to be engaged by the bolt. Since theretaining pawls are part of the tray they remain effective to supportthe rounds in the tray so it is ready to feed ammunition when pivoted tothe operative position.

The outboard side plate 303 of each ammunition tray is designed to beopened for access to the interior of the tray. The side plate ispivotally attached to the forward vertical mounting rod 219 by a bracket304 afxed to the forward end of the side plate and having ears 305through which the mounting rod is inserted. The rear edge 306 of theside plate extends rearward of the ammunition feeding tray so that itmay be gripped to pivot the side plate to the open position.

With the side plate open, the ammunition in the tray may be removed bypulling upwardly on a U-shaped release handle 307. The release handle307 is an extension of a U-shaped connector 309, the ends of which areattached around the guide plate support rod 290. As the release handle307 is pulled, the guide arms 291 pivot outwardly to pull the guideplate spring 288 away from the rounds of ammunition as shown in phantomin FIG. 22. The release handle is also connected to the retaining pawls283 by wires 308 attached to the connector 309. The wires 308 pull theretaining pawls outwardly from under the rounds of ammunition when therelease handle 307 is pulled. The rounds can then be pulled downward outof the tray to unload the gun.

The operation of the gun can best be understood by following through acomplete firing cycle beginning with the gun in the firing positionshown in FIG. 2. When the round is fired, the barrel 5 recoilsrearwardly in the receiver 6. The recoil piston 73 which is aixed to thebarrel moves rearwardly in the stationary recoil cylinder as the barrelrecoils, thereby driving the accelerator piston 93 rearwardly. Since thecross-sectional area of the recoil piston head 75 is larger than that ofthe accelerator piston head 95, e.g. by a ratio of three to two, theaccelerator piston moves rearward faster than the barrel and recoilpiston.

The rear end of the accelerator piston rear extension 107 engages theforward end -of the bolt carrier body 32 to drive the bolt carrierrearward at an accelerated rate relative to the barrel. When the barrellhas, completed an initial part of its recoil, e.g. one-half inch, theaccelerator piston 93 has moved rearward a suicient distance, eg.three-quarters of au inch, to bottom out in the recoil cylinder 70, asshown in FIG. 7. By that time the accelerator piston has impartedsufficient momentum to` the bolt carrier 29 to send the bolt carrier andbolt 2-8 rapidly to the rear of the receiver. Also by then, the forwardface of the recoil piston head 75 has passed the forward edge of thewedge-shaped throttling groove in the cylinder wall, so that the groovebecomes effective to pass fluid around the recoil piston head. Thethrottling groove decreases in cross-sectional area in the rearwarddirection, so that the quantity of fluid which passes through itdecreases at a programmed rate as the recoil piston moves rearward,thereby cooperating with the recoil spring 98 to buffer the recoil forceof the barrel and bring the barrel and recoil piston to a stop with therecoil piston slightly spaced from the accelerator piston forwardextension 101, and the barrel extension 48 slightly spaced from ashoulder 310 on the receiver, as shown in FIG. 8.

As is shown in FIG. 7, during the rst part of the recoil cycle, the bolt28 is locked to the barrel by the locking teeth 160, 161 while the boltcarrier moves rearward at a faster rate than the bolt and barrel and thebolt cam follower pin 162 moves through the rearward axial portion ofthe bolt carrier sleeve cam slots 163. By the time the bolt carrier hastraveled rearwardly with respect to the barrel and bolt suiciently sothat the cam follower 162 of the bolt enters the central portion of thecam slots 163l to rotate the bolt to the unlocked or aligned position,the residual pressure in the barrel chamber has been somewhatdissipated, thereby reducing the friction between the teeth 160, 161 ofthe bolt and barrel. After the bolt is in the aligned or unlockedposition a further short dwell period occurs while the cam pin 162 movesthrough the forward portion of the sleeve cam slots 163. As the cam pinengages the forward end of the cam slots, the bolt moves rearward withrespect to the barrel and the extracting claw 168 which is engaged withthe lip of the expended cartridge, extracts the cartridge from thechamber and carries it rearward with the bolt. Extraction of thecartridge from the chamber occurs between the positions illustrated inFIGS. 7 and 8 so that the barrel is still recoiling, even though it isin its deceleration phase. Thus, the relative velocity between the boltand the barrel as the cartridge is removed, is less than if the barrelwere stopped, so that removal of the cartridge is eased.

When the bolt 28 begins to move rearward away from the barrel, the boltcarrier sleeve 31 is rearward with respect to the bolt, and the crevicepin 165 is urged upward by the spring 164 into the notch 166. After thebolt leaves the barrel, the ramping pin 167 holds the crevice pinengaged in the notch to keep the bolt in the aligned position until itslocking teeth 160 are again engaged in those teeth 161 of the barrel.

Referring now to FIG. 9, as the bolt and bolt carrier continue rearwardwith the cartridge case, the recoil spring 98 and accelerator spring 100urge the accelerator piston 93, recoil piston 73 .and barrel 5 forwardin counterrecoil to the position shown in FIG. 2. During the initialpart of the counter-recoil cycle of the barrel, fluid passes the recoilpiston head 75 both through the wedge-shaped throttling groove 110 andthrough the orifices 123 as the one way flapper valve 122 in the recoilpiston head opens (see FIG. 3a). After the recoil piston head movesforward of the throttling groove 110, only the orices 123 are effectiveto pass fluid through the piston head 75, and therefore the recoilpiston is lthrottled down. The orifices 123 are sized to permit thebarrel to counter-recoil fast enough to be in battery before a new roundis stripped, but slow enough to reduce the impact at the end of thecounter-recoil stroke. As the counter-recoil cycle of the barrel iscompleted, the recoil piston 75 head abuts the counter-recoil Bellevillesprings 127 in the recoil cylinder to butfer the counter-recoil force ofthe barrel and bring it to a stop.

Meanwhile, the bolt and bolt carrier have reciprocated to the rearwardposition shown in FIG. 13 where the expended cartridge is immediatelybelow an ejection port 311 in the upper side of the receiver, and theejecting pin 175 abuts the plunger 186 of the rear buffer assembly. Asthe bolt carrier continues rearward from the position of FIG. 13 to thatof FIG. 14, the bolt 28 and bolt carrier 29 move rearward with respectto the ejecting pin 175, causing the forward end of the ejecting pin tostrike the expended cartridge throwing it loose from the pivotal claw168 and upward out of the ejection port 311. The Belleville springs 182buffer the ejection force.

The rear face of the bolt carrier sleeve 31 engages the plunger 186causing the Belleville springs to compress rearwardly, thereby bufferingthe recoil force of the bolt and bolt carrier. As shown in FIG. 15,.after the recoil of the bolt and carrier is stopped, the Bellevillesprings 1-82 expand and push the bolt carrier forward. If the sear 41 isin the lowered position, as shown in FIG. 15, it engages in the searnotch 42 of the bolt carrier to stop the forward movement of the boltcarrier. As shown in FIG. 16, the sear force is buffered by theBelleville springs 182 of the buffer assembly, since the bolt carrierforces the sear 41 and buffer sleeve 183 forward to compress ytheBelleville springs forwardly against the screw head 188. The parts thencome to rest in about the position illustrated in FIG. l5.

As the bolt carrier reciprocates rearwardly in recoil, the ammunitionfeeding pawls reciprocate upward from the position shown in FIG. 23 tothat shown in FIG. 22, thereby raising a round of ammunition 27a up andinto the feeding station in front of the bolt as shown in FIGS. 20 and22.

If the Sear 41 is disengaged by the trigger 40, or was not in thelowered position at the end of the recoil stroke, the bolt carrier isreturned forward to the battery position by the Belleville springs 182,and the bolt carrier operating spring 200. As the bolt and bolt carriermove forward, the bolt 28 engages the rear of the round of ammunition 27at the feeding station, as shown in FIGS. 21 and 27, and rams the roundforward into the chamber of the barrel.

As the bolt and bolt carrier continue forward toward the position ofFIG. 2, the bolt teeth pass through the locking teeth 161 of the barrelextension and then engage the barrel itself to stop forward movement ofthe bolt. The bolt carrier 29, however, continues forward, camming thecrevice pin 165 out of the notch 166, and rotating the bolt 28 to thelocking position as the bolt cam pin 162 passes through the centralportion of the sleeve cam slots 163. When the bolt carrier reaches theposition illustrated in FIG. 2, the forward end of the bolt carriersleeve 31 strikes the rear end of the barrel extension 48 to stop thebolt carrier. The counter-recoil momentum of the bolt carrier istransmitted through the relatively heavy barrel and the recoil piston73, and is buffered by the Belleville springs 127 in the recoilcylinder. At the same time, the firing pin 173 is driven by the boltcarrier through the opening 174 in the bolt to strike the round ofammunition and tire it, thereby causing the cycle to be repeated.

Referring to FIG. 22, the rounds of ammunition from the right and leftfeeding trays 228, 229 enter the feed station from opposite quadrantswith respect to the barrel axis, while the empty cartridges are ejectedupward into a third quadrant, and the bolt carrier body 32 extendsdownward into a fourth quadrant. Thus, interference between the fastmoving bolt carrier 29 and the rounds 27 is avoided.

It is indicative of the velocities, and forces involved in the operationof this gun, that a typical gun in accordance with this invention isdesigned to re 25 mm. shells at approximately 700 rounds per minute,using a barrel Weighing approximately 50 pounds and a bolt carrier ofapproximately 12 pounds reciprocating at a velocity of about 45 feet persecond.

-Referring now to FIG. 29, an alternative embodiment of the recoil andaccelerator mechanism is shown. That embodiment includes a recoilcylinder 312 and recoil piston 313 connected to the barrel 5 andreceiver 6 in substantially the same manner as the recoil cylinder 70and piston 73 of FIGS. 3a and 3b. The recoil cylinder 312 does notcontain hydraulic fluid, however. An accelerator lever 314 is pivoted inthe receiver at 315 and engages the forward end of the bolt carrier body32. An accelerator piston rod 316, which extends rearward from therecoil piston head 317, is pivotally connected to the arm at 318 by alin-k 319. The ratio of the distance between the two pivotal connections315, 318 on the arm, and the length of the arm, is selected to obtainthe desired rate of acceleration of the bolt carrier body 32 relative tothe barrel 5.

The recoil piston head 317 moves rearwardly in recoil with the barreland during the initial part of the recoil, is resisted only by arelatively weak compression spring 320 rearward of the piston head.After the recoil piston head 317 has moved rearwardly a selected initialdistance, it engages a plunger 322 which abuts a plurality of Bellevillesprings 323 stacked in series-parallel to form a relatively strongspring which buffers the recoil force of the barrel and returns thebarrel to the forward position while the bolt carrier 29 continuesrearward. Counterrecoil of the barrel is buffered by the forwardBelleville spring 324- as in the embodiment of FIGS. 3m and 3b. Thespring and link-type buffering and accelerator system, as illustrated inFIG. 29, is usable in small weapons where the recoil and counter-recoilforces, and the weight of the barrel and bolt carrier are less than inthe gun illustrated in FIG. 2.

FIG. 30 illustrates a control circuit for controlling the rate of fireof the automatic gun, for example between full automatic andsemi-automatic. Frequently full automatic firing is desirable when usinghigh explosive rounds of ammunition. For armor piercing rounds howeverit is usually desirable to fire semi-automatic so that the gun can beaimed for each round.

As can be seen in FIG. 30, a normally open selector switch 330 has anarm 331 engageable by the selector lever 241 to close the switch whenthe selector lever is pivoted to the phantom line position, thus movingthe left-hand ammunition feeding tray 229 containing high explosiverounds into operative relationship with the bolt and feed pawls andmoving the right-hand ammunition feeding tray 228 containing armorpiercing rounds out of operative position. This prepares the gun forautomatic lire.

As seen in FIG. 30, the manual depression of a firing button 332 locatedat a remote control station 334 will continue to energize the firingsolenoid 196 from a battery 336 for so long as the ring button 332remains depressed, provided that the selector switch 330e is closed.This is the automatic ring condition.

If, however, the selector switch 330 is in its normally open conditionfor semi-automatic firing of armor piercing rounds from the right-handfeeding tray, the depression of the firing button 332 at the controlstation energizes the firing solenoid 196 only through the normallyclosed contact 339 of a control relay 341. The control relay 341 isenergized by depressing the firing button 332, however it is relativelyslow acting compared to the firing solenoid 196, the timed relationshipbeing such that the tiring solenoid 196 actuates the trigger 40 to re asingle round prior to the opening of the normally closed contact 339 ofthe control relay.

Thus, the selector switch 330 and associated circuitry, being responsiveto position of the selector lever 241, provides a means for controllingthe firing rate of the gun in accordance with the ammunition storeselected.

I claim:

1. An automatic gun comprising:

(a) a receiver having an ammunition feeding station therein and an'ammunition receiving opening for supplying rounds of ammunition to thereceiver;

(b) a barrel mounted in the receiver forward of the ammunition feedingstation;

(c) bolt means adapted to reciprocate longitudinally in lsaid receiverpast the feeding station, the bolt means having a relatively short upperportion disposed in axial alignment with the barrel and a relativelylong lower portion below the barrel axis, the length of the lowerportion exceeding the stroke of the bolt means;

(d) an inclined cam extending along the length of the lower portion ofthe bolt means; and

(e) ammunition feeding means including:

an -ammunition tray on the receiver, disposed alongside the bolt meansat the feeding station for guiding ammunition upward to the ammunitionreceiving opening,

a pawl carrier interposed between the ammunition tray and the boltmeans, the pawl carrier being mounted for reciprocal vertical movementon the receiver,

feed pawl means on the outboard side of the pawl carrier for engaging around of ammunition below the uppermost round in the ammunition tray tofeed rounds of ammunition upward through the ammunition tray,

a cam follower mounted on the pawl carrier, en-

gageable with the cam on the bolt means to reciprocate the feed pawlmeans, the pawl carrier and the feed pawl means being clear of the pathof the bolt means upper portion throughout the reciprocation of the feedpawl means,

and spring means to urge the uppermost round laterally into the path ofthe bolt means upper portion when the bolt means upper portion hasreciprocated rearward of the ammunition receiving opening.

2. An automatic gun in accordance with claim 1 wherein:

(a) the pawl carrier has forward and rear edges which slide on verticalguides on the receiver;

(b) the cam follower is approximately centered between the forward andrear edges of the pawl carrier; and

(c) the feed pawl means comprises a pair of pawls protruding from thepawl carrier, one forward of the cam follower `and one rearward of thecam follower.

l3. An automatic gun comprising:

(a) a receiver having an ammunition feeding station therein;

(b) a barrel mounted in the receiver forward of the ammunition feedingstati-on;

(c) bolt means adapted to reciprocate longitudinally in said receiverpast the feeding station, the bolt means having a relatively short upperportion disposed in axial alignment with the barrel and a relativelylong lower portion below the barrel axis, the length of the lowerportion exceeding the stroke of the bolt means;

(d) an inclined cam extending along the length of the lower portion ofthe bolt means;

(e) an ammunition tray disposed alongside the receiver at the feedingstation for guiding ammunition upward to the feeding station, theammunition feeding tray having yan inner side wall disposed adjacent thereceiver, an ammunition discharge opening in the inner side walladjacent the feeding station and in alignment with the upper portion ofthe bolt means, said ammunition discharge opening having ya rear portionnarrower than the diameter of an ammunition round through which theround may protrude a limited distance for engagement by the bolt and anenlarged forward portion through which the round may pass upon beingengaged and moved forward by the bolt and the ammunition tray havingfeed pawl openings in its inner side wall disposed below the ammunitiondischarge opening;

=(f) a pawl carrier interposed between the ammunition tray and the boltmeans, the pawl carrier Ibeing mounted for reciprocal vertical movementon the receiver;

(g) feed pawls on the outboard side of the pawl carrier in alignmentwith feed pawl openings in the ammunition tray for engaging rounds ofammunition therein to feed them upward through the ammunition traytoward the ammunition discharge opening;

(h) a cam follower mounted on the pawl carrier, en-

gageable with the cam on the bolt means to reciprocate the pawl carrier;

(i) means pivotally connecting the forward end of the ammunition feedingtray to the receiver; and

(j) means for selectively holding the ammunition feeding tray in eitherof two pivotal positions relative to the receiver, a first positionwherein the tray is disposed adjacent the receiver in cooperativerelation with the bolt means and the feed pawls and a second positionwherein the tray is disposed away from the receiver and out ofcooperative relation with the ibolt means and feed pawls.

4. The automatic gun of claim 3 wherein the ammunition feeding trayincludes:

(a) spring means therein for urging rounds of ammunition toward thedischarge opening;

(b) spring loaded pivotal retaining pawls therein for holding linkedrounds of ammunition against downward movement; and

(c) a mechanical linkage coupled to the spring means and holding pawlsand accessible on the outboard side of the feeding tray for releasinglinked rounds of ammunition for movement downward and out of the feedingtray.

5. An automatic gun comprising, in combination;

(a) a receiver;

(b) ammunition feed means for selectively feeding rounds of ammunitionto the receiver from any of a plurality of different ammunition stores;

(c) gun sighting means; and

(d) means for adjusting the gun sighting means responsive to theammunition store selected bv the feeding means.

6. An automatic gun comprising, in combination:

(a) a receiver;

(b) ammunition feed means including selector means for selectivelyfeeding rounds of ammunition to the receiver from any` of a plurality ofdifferent ammunition stores;

(c) means controlling the firing rate of the gun; and

(d) means operably connecting the firing rate controller to the selectormeans for firing the gun at one rate responsive to selection of oneammunition store and at a different rate responsive to selection ofanother ammunition store.

7. An automatic gun comprising:

(a) a receiver having an ammunition feeding station therein;

(b) a barrel mounted in the receiver forward of the ammunition feedingstation;

(c) first ammunition guide means axed to the receiver for guiding roundsof -ammunition to the feeding station from a rst quadrant with respectto the barrel axis;

(d) second ammunition guide means affixed to the receiver for guidingrounds of ammunition to the feeding station from a second quadrant withrespect to the barrel axis;

(e) bolt means adapted to reciprocate longitudinally in said receiverpast the feeding station, the bolt means having a portion in line withthe barrel axis and a portion offset from the barrel axis, said offsetportion being disposed in a third quadrant with respect to the barrelaxis;

(f) means for ejecting expended cartridge cases from the bolt means intothe fourth quadrant;

(g) means for selecting either of the ammunition guide means; and

(h) means on said offset portion of the bolt means for driving anammunition feed means to positively feed ammunition from the selectedguide means to the ammunition feeding station responsive toreciprocation of the bolt means.

8. An automatic gun comprising, in combination:

(a) a receiver having an ammunition feeding station therein;

(b) a barrel mounted in the receiver forward of the ammunition feedingstation;

(c) means adapted to reciprocate longitudinally in said receiver pastthe feeding station, the reciprocating means having a relatively shortupper portion and a relatively long lower portion, the lower portionbeing longer than the stroke of the reciprocating means and having apair of cams extending along its length on opposite sides thereof; and

(d) ammunition feeding means for selectively feeding ammunition to theammunition feeding station from either of two stores, said ammunitionfeeding means including, two feed pawl means each adapted to feedammunition from a different one of the stores, and two cam followermeans each cooperating with a different one of said cams to operate oneof the feed pawl means; and

(e) selector means for activating one or the other of said two feed pawlmeans to feed ammunition from a selected store.

9. The automatic gun of claim 8 wherein the ammunition feeding meansincludes:

(a) a pair of ammunition guide trays attached to the receiver anddisposed on opposite sides thereof, each guide tray being selectivelymovable to an operable position beside the ammunition feeding station;and

(b) a pair of pawl carriers mounted in opposite sides of the receiveradjacent the guide means for vertical reciprocation toward and away fromthe feeding station, each pawl carrier having one of the cam followermeans mounted on its inboard side, and one of the feed pawl meansdisposed on its outboard side for engaging the rounds of ammunition inthe adjacent ammunition tray when the tray is in the operable position.

10. The automatic gun of claim 9 further comprising:

(a) means pivotally connecting the forward ends of the ammunition guidetray to the receiver;

(b) selector means coupled to the receiver and to the rear ends of theammunition trays for adjusting the trays to any of three pivotalpositions relative to the receiver, a first position wherein solely onetray is operably engaged with its associated feed pawl means on thereceiver, a second position wherein solely the other tray is operablyengaged with its associated feed pawl means on the receiver, and a thirdposition wherein neither tray is operably engaged with the associatedfeed pawl means.

11. An automatic gun comprising:

(a) a receiver having an ammunition feeding station and at least twoammunition receiving openings located adjacent the feeding station ondifferent sides of the receiver for supplying roundsof ammunition to thereceiver;

(b) at least two ammunition feed trays positioned on different sides ofthe receiver proximate to said ammunition receiving openings andattached to the receiver for supplying successive rounds of ammunitionfrom different stores through the separate openings to the feedingstation;

(c) a carrier mechanism which reciprocates longitudinally of thereceiver for stripping successive rounds of ammunition from the feedingstation and chambering them in the barrel;

(d) a feed pawl operatively associated with each feed tray driven by thecarrier mechanism to advance rounds of ammunition through the tray; and

(e) a selector mechanism movable between different positions forengaging and disengaging the different feed pawls from operativerelationship for selectively operating either of said ammunition feedtrays.

12. An automatic gun comprising, in combination:

(a) a receiver;

